On our boat, areas that suffer(ed) the most wear and tear seem to be around
galley and
navigation station. On those areas, there are two kinds on parts that require very different kind of treatment. What is solid
teak, is very easy to work with. Just sand or scrape off the worn out surface and give it the layers of new varnish. Easy and straightforward, hard to make
mistakes. Sime parts, like drawers and cabinet doors, can also easily be taken out and fixed at home garage or some place else not filling the boat with dust and fumes.
The hard part is the plywood sections. On most plywoods, the teak layer is fairly thin. At least for me, it is hard to make judgement, if it is only the varnish that is already gone, or has the teak film worn out, too. Sand it just a bit too much, and you have a new problem - no teak. Sure enough, you can tint your varnish, but it is a longish path of trial and error before the colors will match. However, you and I are certainly not the first persons with this issue, so I think it would be fair to assume, that teak or mahongy tinted varnishes should be available on
paint stores and chandleries with a reasonable variety on shades available.
One more hint. Just start with the solid teak sections that look the worst. Every piece that has been fixed makes the the entire boat look better. Sure enough you can do it all at once, but you can also take it slowly. Just every time you leave the boat, do something small. By the next day/time you come back, the fumes are gone and you can keep on sailing.